Thin People at Much Higher Risk of Death After Surgery

Slender people are more likely to die after surgery than those who are overweight, a new study finds.

People with a body mass index (BMI) of 23 or less were 40 percent more likely to die within a month of a surgical procedure, compared with people whose BMI was between 26 and 29.

BMI is an indicator of body fatness. A BMI less than 18.5 is considered underweight, between 18.5 and 24.9 is normal weight, between 25 and 29.9 is overweight and above 30 is obese, according to the Centers for Disease Control and Prevention.

The results held even after the researchers took into account the condition the patient had that required surgery, and the risk of death associated with that surgery.

The findings suggest that low BMI should be recognized as an important risk factor for death following surgery, said study researcher George Stukenborg, of the University of Virginia’s School of Medicine. Doctors should take into account thinness when planning a patient's care after surgery, and should tell thin patients about their increased risk of death, Stukenborg said.

Death after surgery

Several earlier studies have found that being obese did not increase people's risk of dying after surgery. In fact, some studies have suggested that being overweight or moderately obese might protect against death after surgery. However, many of these studies were small and had a short follow-up period, Stukenborg said.

In the new study, Stukenborg and colleagues analyzed information from more than 189,500 patients from 183 centers who underwent surgery between 2005 and 2006.

The researchers divided patients into five groups based on their BMI. They calculated the risk of death for each group as compared to the risk of death for those in the middle group (with a BMI between 26.3 and 29.7).

About 3,200 patients died within 30 days of surgery. Among those with a BMI of 23.1 or less, 2.8 percent died within 30 days, whereas 1.5 percent of patients with a BMI between 26.3 and 29.7died.

There was no difference in the risk of death between patients who were overweight, and patients who were obese or very obese, the researchers found.

Why the link?

This study cannot tell us why thin people are at an increased risk of death after surgery, Stukenborg said. One idea is that these patients may be more frail, or may have recently experienced weight loss, Stukenborg said.

The researchers want to conduct further studies to find what puts thin patients at risk, Stukenborg said.

The study is published online today (Nov. 21) in the journal Archives of Surgery.

Pass it on: Being thin may be a risk factor for death following surgery.